Recently, Liquid Crystal Display (LCD) products develop very rapidly, and more and more liquid crystal displays with high quality gradually list in the market and are applied in wider fields.
The principle for displaying images by a liquid crystal display is that: liquid crystal are deflected by a certain angle to pass light through when a voltage is applied across two plates sandwiching the liquid crystals, and the light transmissivity of the liquid crystal depends on the size of the deflected angle of the liquid crystal, thus different gray scales are displayed.
However, the electrical potential at a common electrode is fixed during the displaying period of the liquid crystal display, and the layer of the liquid crystal is equivalent to a capacitor. When a Driver Integrated Circuit (Driver IC) is illuminated by light and then a photovoltaic effect is caused in the Driver IC, carriers such as electrons generated by the photovoltaic effect enter into a data line and change electrical charges in the data line, and hence electrical charges at a pixel electrode and the common electrode are changed, at this time, a voltage across the pixel electrode and the common electrode is changed, so that a second voltage generated by the photovoltaic effect is formed across the pixel electrode and the common electrode to form an electrical field, the electrical field is caused by residual ions and thus also referred to as a residual electrical field. When the LCD emits light again, the original symmetrical voltage applied across the pixel electrode and the common electrode is applied in combination with such residual electrical field in the LCD, resulting in an asymmetrical voltage applied in the LCD, and the asymmetrical voltage will lead to flicker of the LCD. For now, the photovoltaic effect may be prevented by a shading tape (or a black tape); but after attaching of cover lens onto a capacitance touch screen becomes popular, the shading tape is abandoned, instead, an opaque area is designed on the cover lens of the capacitance touch screen to shield light. However, in producing and manufacturing the LCD, the opaque area on the cover lens cannot shield light very well, thus the photovoltaic effect still exists and causes a negative effect to the display quality.